This application claims the priority of Korean Patent Application No. 2002-16692, filed on Mar. 27, 2002, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of the Invention
The present invention relates to a system and method for detecting a three-dimensional direction of a sound source.
2. Description of the Related Art For understanding of the present invention, a sound source, which is an object of direction estimation of the present invention, will be referred to as a speaker and will be illustratively described below.
Microphones generally receive a speech signal in all directions. In a conventional microphone referred to as an omnidirectional microphone, an ambient noise and an echo signal as well. as a speech signal to be received are received and may distort a desired speech signal. A directional microphone is used to solve the problem of the conventional microphone.
The directional microphone receives a speech signal only Within a predetermined angle (directional angle) with respect to an axis of the microphone. Thus, when a speaker speaks at the microphone within the directional angle of the directional microphone, a speaker's speech signal louder than the ambient noise is received by the microphone, while a noise outside the directional angle of the microphone is not received.
Recently, the directional microphone is often used in teleconferences. However, because of the characteristics of the directional microphone, the speaker should speak at the microphone only within the directional angle of the microphone. That is, the speaker cannot speak while sitting or moving in a conference room outside the directional angle of the microphone.
In order to solve the above and related problems, a microphone array system which receives a speaker's speech signal, while the speaker moves in a predetermined space, by arranging a plurality of microphones at a predetermined interval, has been proposed.
A planar type microphone array system as shown in FIG. 1A is installed in a predetermined space and receives a speaker's speech signal while the speaker moves toward the system. That is, the planar type microphone array system receives a speaker's speech signal while the speaker moves within a range of about 180° in front of the system. Thus, when the speaker moves behind the microphone array system, the planar type microphone array system cannot receive a speaker's speech signal.
A circular type microphone array system which overcomes these major limitations of the planar type microphone array system, is shown in FIG. 1B. The circular type microphone array system receives a speaker's speech signal while the speaker moves within a range of 360° from the center of a plane where the microphone is installed. However, when the microphone plane is the XY plane, the circular type microphone array system considers a speaker's location only in the XY plane while the Z axis location of the speaker is not considered. As such, the microphone receives signals from all planar directions and a noise and an echo signal generated along the Z axis, and thus there is still distortion of the speech signals.